Precisely. Many components don't have a straight, or linear, I-V characteristic. Physically, as the voltage across a PN junction (a diode) increases, the "depletion region" between the PN junction shrinks, leading to, effectively, lower resistance overall. I like to look at it as though resistance decreases with voltage, so the current increases exponentially with voltage. I'll probably be yelled at for saying that, but it works for me.

Precisely. Many components don't have a straight, or linear, I-V characteristic. Physically, as the voltage across a PN junction (a diode) increases, the "depletion region" between the PN junction shrinks, leading to, effectively, lower resistance overall. I like to look at it as though resistance decreases with voltage, so the current increases exponentially with voltage. I'll probably be yelled at for saying that, but it works for me.

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Well, incrementally, I would agree that small signal ac resistance increases as the diode is biased upward on the I-V curve. But re "resistance" in the general sense, I don't think I agree with you.

LEDs and diodes are classified as non-ohmic or non-linear, but they still have resistance to a DC current flow and dissipate power as determined by V * I at their operating point. They have a non-linear resistance.

LEDs and diodes are classified as non-ohmic or non-linear, but they still have resistance to a DC current flow and dissipate power as determined by V * I at their operating point. The have a non-linear resistance.

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Of course, I was just saying that you cannot regard diode "resistance" the same as in the general Ohmic sense. It is non-linear, & varies with I-V operating point, as well as temperature. An equation or graph is needed to understand the device fully, as the simple R = V/I relation does not hold.